1. Field of the Invention
The present invention relates to detergent-dispersant additives for lubricating oils, to methods for preparing such additives and to lubricating compositions comprising such additives. More particularly, the detergent-dispersant additives of the invention have a base of sulfurized and overalkalinized alkylphenate sulfonates derived from alkylphenol sulfonic acids. The additives of the present invention are resistant to hydrolysis and function as anti-oxidants.
2. Description of the Prior Art
Alkaline earth metal salts of alkylphenol sulfonic acids having a high content of sulfonate functional groups are known to be useful as dispersant additives for lubricating oils. Such uses are described, for example, in French Pat. No. 2,062,671 the disclosure of which is hereby incorporated herein by reference. These additives suffer from the disadvantage of not functioning as anti-oxidants.